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A tetrahedral polyelectrolyte brush in the presence of trivalent counterions is researched under the condition of good solution by means of molecular dynamics simulations. Grafting density and charge fraction are varied to generate a series of surface patterns. Lateral microphase separation happens and various interesting pinned patches appear at appropriate charge fraction and grafting density. Through a careful analysis on the brush thickness, the pair correlation functions, the distributions of net charge, and the four states of trivalent counterions in the brush, we find that the ordered surface patterns and special properties are induced by the pure electrostatic correlation effect of trivalent ions even in the good solvent. Furthermore, the dependences of electrostatic correlation on the charge fraction of tethered chains are evaluated for fixed grafting density. Also, our results can serve as a guide for precise control over the stimuli-responsive materials rational and self-assembly of nanoparticles. [ABSTRACT FROM AUTHOR]

A diquinoxalinopyrene ( DQP) derivative and the corresponding oligomers ( PDQPs) with M of ca. 3300, 4200, 5600, and 7300 have been synthesized. It is found that the band gaps and highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels between DQP and its homopolymers only have a slight difference, implying a limited conjugation extension achieved from unimer to heptamer. The DFT calculation is in accordance with the experimental results. It reveals that the nodal planes are across the 2,11-positions in the LUMO and/or HOMO of DQP, dimer and trimer, which can be used to explain this special phenomenon. [ABSTRACT FROM AUTHOR]

A kind of fibrous clay, palygorskite (PAL), was used as the sole stabilizer in suspension polymerization without the using of any other stabilizer usually used, especially polymeric stabilizers. In order to improve the compatibility with the organic monomer, PAL nano fibers were organically modified with silane coupling agent methacryloxypropyltrimethoxysilane (MPS). Transmission electron microscopy (TEM) and Fourier-transform infrared (FTIR) spectroscopy results show that the hydrolyzed MPS was attached onto PAL surface through Si-O-Si bonds formation without morphology change of PAL. At a loading amount of PAL to monomer as low as 0.36 wt%, effective stabilization could be achieved. After suspension polymerization, spherical poly(methyl methacrylate) (PMMA) particles were obtained. Scanning electron microscopy (SEM) analysis on both the outer surface and the inner cracked surface of the spherical PMMA particles indicates that the PAL particles reside on the surface of the PMMA spheres. The densely stacked PAL together with attached silane coupling agent stabilized the droplets throughout the suspension polymerization. [ABSTRACT FROM AUTHOR]